RP: Investigating Flux Linkage on a Search Coil

• What is the overall aim of the experiment?

  Determine how magnetic flux linkage varies
• How is the magnetic flux linkage varied in the experiment?

  By rotating a search coil in a magnetic field
• What is the independent variable in this experiment?

  Angle between the normal and magnetic field
• What is the dependent variable in this experiment?

  Induced e.m.f, ε
• What are the control variables in the experiment?

  • Area of the search coil, A
  • Number of loops on both coils, N
  • Magnetic field strength, B
  • Frequency of the power supply, f
• What is the resolution of the protractor used in the experiment?

  1º
• What is the resolution of the CRO used in the experiment?

  2 mV / div
• What is the method for setting up the experiment?

  1. Arrange the apparatus as shown in the diagram.
  2. Connect the slinky spring to the alternating power supply.
  3. Set up the CRO to show amplitude only.
  4. Position the search coil halfway along the slinky spring.
  5. Orient the search coil parallel to the slinky spring.
  6. Record the induced e.m.f from the CRO trace.
  7. Rotate the search coil by 10º and repeat.
• What should be recorded from the CRO trace?

  The peak-to-peak voltage, V
• How is the peak e.m.f, ε, calculated from V?

  Halve the peak-to-peak voltage, V
• What is the maximum angle to which the search coil is rotated?

  90º
• What is the expression for induced e.m.f in the search coil?

  ε = −B0ANωsin(ωt)cos(θ)
• What does NΦ represent in the context of the experiment?

  Magnetic flux linkage through the search coil
• How is the angular frequency, ω, related to frequency, f?

  ω = 2πf
• What happens to the flux linkage when using an AC source?

  It oscillates at the same frequency as the AC source
• What is the relationship between current and magnetic flux density?

  Magnetic flux density is proportional to current
• What is Faraday's law used for in this experiment?

  To find the peak induced e.m.f in the search coil
• What does the expression ε0 = B0ANωcos(θ) represent?

  Peak induced e.m.f in the search coil
• How does the graph of peak e.m.f ε against cos(θ) appear?

  • It should be a straight-line graph.
  • Shows induced e.m.f is proportional to cos(θ).

  
• What are the systematic errors in the experiment?

  • Calibration of the search coil is needed.
  • Field lines may not be perfectly aligned.
  • Parallax error from reading angles.
• What are the random errors in the experiment?

  • Repeat for a full turn (θ = 360°).
  • Use a calibrated motor for rotation.
  • Use blu-tack for protractor stability.
• What safety considerations should be taken during the experiment?

  • Keep fluids away from electrical equipment.
  • Check for damaged wires and fuses.
  • Do not exceed current rating for the coil.
  • Limit current duration to prevent overheating.